Which of the following options is/are true?

1. A.

   Some K- regular graph can be complete graph

2. B.

   In a simple connected graph with more than 2 vertices, it must have at least 2 vertices with same degree.

3. C.

   A graph G is bipartite if and only has even cycle.

4. D.

   The degree sum of odd degree vertices must be odd.

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